
Communication cost is a key issue to be solved before deploying FLchain systems in practice.
blackMost of current FLchain schemes analyze communication costs by considering on-device training latency, latency of communication with miners, and mining latency [1]}, [2]}, while the work in [3]} focuses on edge computing latency and parameter transfer communication latency.

Some possible solutions can be adopted to achieve lower communication costs, such as reward-based training [2]} and adjustment of block arrival rate [3]} with respect to learning accuracy and bandwidth resource constraints.

Most of current solutions [1]}, [2]} rely on the PoW consensus mechanism, which often requires large bandwidth and energy resources to implement the mining process. Therefore, developing lightweight blockchains should be considered to facilitate FLchain [8]}, aiming to enhance the users' experience of training and reduce system costs.

